Present day research and development activities on superconductors have given much attention to the fact that there are peculiarities in the behavior of a superconductor with respect to the electrical resistance and magnetization. These researches, starting from metallic superconductors of alloys and chemical compounds, have expanded its limits to include organic compounds as well. As at present, them are about 50 kinds of organic compounds that show superconducting transition, their critical temperatures being at the most about 45K.
Even among the organic compounds, the compound BEDT-TFF attracts much attention for the reason that BEDT-TTF can act as a common constituent in preparing various complexes of insulators, metals and superconductors. The structural formula for BEDT-TTF is shown in FIG. 1.
A BEDT-TTF compound of the form (BEDT-TTF).sub.2 X shows several superconducting phenomena, and the critical temperatures for such phenomena have a positive correlation to the volume (or rather the effective volume) occupied by the conduction layers that contain BEDT-TFF. In order to increase the effective volume, now it has come to the stage of searching for anions, which constitute a large frame work for conduction layers.
Research and development efforts on preparation and observation of cyanometalates and thiocyanometalate compounds of BEDT-TTF have produced substances such as k-(BEDT-TTF).sub.2 [Cu(NCS).sub.2 ], (BEDT-TTF).sub.2 [NH.sub.4 Hg(SCN).sub.4 ], k-(BEDT-TTF).sub.2 [Ag(CN).sub.2 ]H.sub.2 O, which are known to show superconductivity.
The molecular arrangement of BEDT-TFF is determined by the framework of anions X.sup.-, which determine the electronic state of the compounds. These anions that set up the framework for BEDT-TFF are the key to controlling the electronic state, or in other words, they are the key to the discovery of superconductors. It can be predicted that there exist substances that are superconducting and that are the compounds of cyanometalate or thiocyanometalate anions with BEDT-TFF, which have the tendency to form a cluster or polymer so that the effective volumes are large.
Similar to thiocyanometalate anions that are contained in BEDT-TTF complexes that show superconducting transition, the cyanate anions have the nature of forming coordination bond with transition metals or forming hydrogen bonds with molecules of water. In BEDT-TTF compounds, there are instances of the BEDT-TTF arrangement being controlled by pseudo-halogenate anions, which form anion clusters or polymers. The electronic state attained as a result of this BEDT-TFF arrangement provides several superconductors.
The present invention has the objective of obtaining a novel BEDT-TTF type organic material, because it is considered that BEDT-TTF is an effective multi-purpose material that develops superconductivity.